Safety coupling for flexible shafting



Sept. 14, 1954 w, JONES 7 2,688,857

SAFETY COUPLING FOR FLEXIBLE SHAFTING Filed July 29. 1953 I N V E N TOR.4/562? #4 Jan/5.9

Patented Sept. 14, 1954 SAFETY COUPLING FOR FLEXIBLE SHAFTIN G Joseph W.Jones, New York, N. Y., assignor to Jones Motrola Corporation, Stamford,Conn., a corporation of Connecticut Application July 29, 1953, SerialNo. 371,081

1 Claim. 1

The invention herein disclosed relates to flexible shaft drives fortachometers and instruments of like character.

Particularly, the invention is concerned with the drive of tachometersused with diesel engines and certain types of quick starting electricmotors.

These machines start so suddenly and at such instant high speed as totend to break the flexible shafting and drive connections to thetachometer.

In the case of the diesel engine, if the sudden start does not break orinjure the drive connections or the instrument operated thereby, theeffect may be to momentarily overspeed the tachometer which, in the caseof automatic cutoff actuated by the tachometer, would have the effect ofstopping the engine even before it was properly started.

Special objects of this invention are to provide simple and practicalmeans, readily adaptable to present installations, which will preventsuch overspeeding and which, in general, will protect the entire line ofdrive connections and serve as a safe, effioient drive for thetachometer, or other such instrument.

Further special objects of the invention are to incorporate the safetyfeatures mentioned in a small, lightweight form of slip clutch,adaptable to the end of the flexible shafting and directly engageablewith the squared end shaft of the conventional tachometer.

Other desirable objects and the novel features through which thepurposes of the invention are attained are set forth and will appear inthe course of the following specification.

The drawing accompanying and forming part of the specificationillustrates a present practical embodiment of the invention butstructure may be modified and changed within the true intent and scopeof the invention as hereinafter defined and claimed.

Fig. 1 in the drawing is a broken part-sectional side elevation of theinvention as applied to a flexible drive cable and connected with atachometer of usual or standard design.

Figs. 2 and 3 are enlarged broken details of the coupling applied to theend of the flexible drive shaft; Fig. 2 indicating this coupling asengaged with the squared stem of the tachometer shaft and Fig. 3 showingthese parts in separated relation.

Fig. 4 is a cross-sectional view on substantially the plane of line 4-4of Fig. 2.

Fig. 5 is a similar view but showing the parts in the slip-driverelation.

The instrument indicated at I in Fig. 1 may be considered a tachometerof conventional design, having a drive shaft 8 terminating in a squaredportion 9 engageable by a clutch or coupling element on the end of theflexible drive shaft II).

In the present invention, this coupling is in the form of a sleeve ortubular body portion H swaged or otherwise secured on the end of theflexible shaft and having a circular socket 12 in the end of the samelarge enough to rotatably receive the angular end portion 9 of theinstrument shaft.

At opposite sides the socket forming portion l2 has transverse recesses13 which are cut through and open into the socket.

A washer or collar i4 is loosely engaged over the terminal sleeve H andthis collar has angularly extended spring fingers It at opposite edgesof the same, provided with inwardly indented end portions [6 whichproject inwardly into the openings at IS in the sides of the socket andfar enough to engage the fiat sides of the tachometer stern. Thisrelation is shown in Fig. 4.

The spring coupling described may be made of a single piece of springsheet metal, pierced at the center to pass over the sleeve l l andhaving the extensions [5 projecting from opposite edges and bent up atan angle and extended inwardly to enter the notches at the oppositesides of the socket I2.

This spring element can thus be mounted and be yieldingly secured inplace by simply slipping it over the sleeve into position where theinwardly extended ends of the spring fingers will enter the openings inthe sides of the socket. In this relation the ends of the spring fingerswill engage opposite flat sides of the tachometer shaft to form a driveconnection for all normal operations.

In case of any suddenly applied torque, however, the spring fingers willopen up or yield outwardly, as in Fig. 5, to release the grip on thesquared shaft and to permit the coupling to turn until such time as theyagain pick up and carry the tachometer shaft along with it.

The invention provides a spring safety coupling which, as shown in Fig.1, may 'be applied to an ordinary flexible shaft drive and used with atachometer, or like instrument, of conventional design, the springcollar being light enough and small enough to go on the end of the shaftand to be received within and operate in the usual neck portion ll ofthe instrument.

What is claimed is:

A safety slip coupling for the flexible shaft 3 drive of a tachometer orthe like, comprising a sleeve attachable to a flexible shaft, saidsleeve having a circular socket in the end of the same, of a size tofreely receive the squared shaft end of a conventional tachometer, saidsocket having openings in opposite sides of the same and a collar ofspring metal engaged over said sleeve and having angularly extendedspring fingers at opposite edges of the same, terminating in inwardlybent ends entered into said openings far enough to engage the fiat sidesof the squared shaft end and to retain said collar in position on thesleeve.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,503,189 Blba, Jr Apr. 4, 1950 2,537,122 Desmond Jan. 9, 19512,656,185 Bach Oct. 20, 1953

